Popup is rendered transparent

Popup component from the UI class is rendered transparent and without any border. Please run the following snippet to see the issue.

let nRowCount = 1000;
let nColCount = 100;
let ggrid = grok.shell.addTableView(grok.data.demo.randomWalk(nRowCount, nColCount)).grid;

let button = null;
let btn = ui.button('Click', function(){

    let eContent = ui.splitV([ui.divText("AAAAAAAAAAAAAAAAAAAA"), ui.divText("BBBBBBBBBBBBBBBBBBB")]);
    let popup = ui.showPopup(eContent, button, true);

button = btn;
ui.dialog("Popup Bug Demo").add(btn).show();

Thant is actually correct,
made to allow you to fully customize your popup without extra !important overrides.

We could add an option to showPopup method, that controls style, so you can choose between bare popup div and style it as you wish, and some initial styling.

I think Dmitri is right, since we exposed is as an API function it has to have a decent default styling, application developers should not worry about that unless they really want to.